1. Soil Morphology Willie Harris apatite@ufl.edu Acknowledgments:
Wade Hurt
Mike Vepraskas
FAESS Soil Scientists
Website to download files of talks:
wgharris.ifas.ufl.edu.hsw.htm

2. Properties used in describing soil layers
a. Color: A key property in hydric soil interpretation
Most evident
Influenced by OM and redox-sensitive metals
Wetness affects OM and redox-sensitive metals

3. Color is described using the Munsell Color Book
Here, the
book is opened
to the 10R
Page …

4. Hue:
Related to
Wavelength
Value:
Related to
reflectance
Chroma: Degree of spectral purity

5. Here, the
book is opened
to the 10YR
Page …
Notation works
Like this:
yellowish brown (10YR 5/6)
value
hue
chroma

6. Hue Red 0 2.5R 5R 7.5R 10R Yellow-Red 0 2.5YR 5YR 7.5YR 10YR Yellow
Hues highlighted in yellow are the common soil hues.
Y 5Y 7.5Y Y

7. Value The Lightness or Darkness of Spectral Color 10/0 - Pure White
5/0 - “Gray”
0/0 - Pure Black
The Lightness or Darkness of Spectral Color

8. Chroma “Neutral” “Pure” Color Color /0 /2 /4 /6 /8
/ / / / /8
Increasing strength of color
Increasing grayness

9. Reading Soil Colors Optimum conditions Natural light Clear, sunny day
Midday
Light at right angles
Soil moist

10. Contrast of Colors Faint -- evident only on close examination
Contrast refers to the degree of visual distinction between associated colors.
Faint -- evident only on close examination
Distinct -- readily seen
Prominent -- contrast strongly
Hydric soil indicators specify distinct or prominent.

11. Abundance and Size of Color Contrasting Areas
Few -- less than 2%
Common -- 2 to 20%
Many -- more than 20%
Fine -- < 5 mm
Medium -- 5 to 15 mm
Coarse -- > 15 mm
Abundance more important for Hydric Soils

12. b. Texture - proportions of sand, silt, and clay
The mineral component is usually described by it’s texture. Soil texture refers to the relative amounts of the variously sized soil separates. Where:
Gravel and larger fragments are >2 mm in diameter.
Sand is mm in diameter.
Silt is 0.05 to mm in diameter.
Clay is < mm in diameter.

13. Relative Sizes of Soil Particles
Sand ( mm)
Silt ( mm)
Clay (<0.002 mm)

14. USDA Textural Classes - Defined by “textural triangle”

15. c. Structure: Way soil particles aggregate into larger units with planes of weakness between them. Individual aggregates called peds.
Common surface structure is granular: small spheroids
Examples of common subsurface structure:
Prismatic or
Columnar
Blocky
Platy

16. Soil Horizon Designations
Soil horizons are layers formed via soil processes
Master Horizons
O – High organic matter content; “organic soil material”!
A – Enriched in organic matter content; but not “organic soil material”!
– At surface or below O
– May be an “A” if disturbed (e.g., plowing)
E – Loss of fine-textured components; “eluviation”
– Characterized by clean sand, light color (high value, low chroma)
B – Accumulation of components translocated from above
– In-situ accumulation of metal oxides
– Other in-situ gains and losses
C – Little or no alteration; rock structure often evident
R – Rock

17. Transition Horizons

18. Subordinate Distinctions within master horizons
Convey information about soil genesis and disturbance
Designated by lower case. EX: Bt, Bw, Ap
Important ones for Florida:
Ap - plowed or disturbed surface
Bt - illuvial accumulation of clay
Btg - illuvial clay + iron reduction or depletion
Bh - illuvial accumulation of aluminum and carbon
Oi - fibric organic soil material
Oe - hemic organic soil material
Oa - sapric organic soil material

19. Horizon Boundaries

20. Bringin’ it all back home
A YR 3/1; sand; cw boundary
E YR 5/2; sand; gw boundary
E YR 7/1; sand; as boundary
Bh - 5 YR 2/1; sand; gw boundary
Btg YR 5/2; sandy clay loam;
gw boundary; blocky structure
Btg YR 6/2; sandy clay loam;
blocky structure